The images -- taken between the 1950s and 1990s -- went viral, and Maloof, who at first thought he had stumbled upon the opus of a seasoned photojournalist, started tracking down more of Maier's photographs. He later created the Maloof Collection, which encompasses 90% of Maier's work.
Since then, the reclusive nanny's images of grit and glamor of the urban landscape have been exhibited around the world, drawing comparisons to the great photographers of 20th century, such as like Robert Frank and Diane Arbus. Her mysterious life spurred Maloof to make a documentary, called Finding Vivian Maier, which is currently in cinemas.
"There are two sides to her allure," says Maloof. "The photos are really good, and it's almost like viewers are discovering a piece of history, which is exciting. The other part is that her story is really fascinating and mysterious, and people like a good mystery.
"They are intrigued by it and want to solve it."
Rogers also attributes the wave of interest in Maier's work to the revival of street photography, where photographers capture what they see with no staging or construction.
"People see it as very honest and reflective of the abilities of the photographer, and there is a great resurgence of this style right now," she said.
Maier would sometimes bring her young charges along on her long exploratory walks, on one occasion taking a little girl to Chicago's stockyard where in the 1950s corpses of trampled sheep were a common sight.
"She exposed the children of wealthy families to the grit of urban life," said Maloof. "In that way they perhaps got a taste of how the world really is outside their sheltered, privileged communities."
Part of Maier's great skill was in capturing the full breadth of urban life, effortlessly switching between images of deprivation and glamor.
There is an intimacy in Maier's photos, which may have been aided by her use of the Rolleiflex camera which is held at chest level, allowing her to look straight at the people she was photographing. "There is trust between Maier and her subjects, and the photos have great intensity -- perhaps because she was maintaining eye contact with them," said Rogers.
While she is primarily known for her black and white images, Maier also left a small, but equally impressive, body of work in color.
Maier's perceptiveness was perhaps also shaped by the early years she spent in France, allowing her to observe details of American life with the particularly sharp eye of an outsider.
"Her sensibility was certainly very European," says Rogers. "At the time when she lived there, Europe was the center of the sort of humanistic photography she would go on to create."
A number of Maier's photographs feature some of the most celebrated personalities of her era, such as Audrey Hepburn, Frank Sinatra, and in this picture, Kirk Douglas.
"She was a film buff, she knew a lot about foreign films and where all the premieres were taking place," says John Maloof. "She would also go to book signings and take photos of the authors."
Maier's thirst for culture took her on a round-the-world trip, and she visited Europe, the Middle East, Asia and the Caribbean. As with most things in her life, Maier undertook the journey alone, and staying true to her subject matter, her lens was again drawn to the downtrodden and dispossessed people she came across.
The quality of her prints was of great importance to Maier, and she would always send them to France to be developed. However, one of the great unanswered questions about her story is why, after taking over 150,000 images in her life time, she decided not to show them to anyone.
"She understood her works were quite special, but perhaps she didn't want people telling her what to do with them," says Rogers. "Although it does seem strange that she wouldn't have wanted to share her view and vision of the world with other people."
Rogers adds that the profession of a nanny, a person always present but never the focus of attention, probably allowed Maier to take a step back and have an unfettered perspective of the world.
"She was a solitary individual but this made her a great observer. She never got married she was very proud that she was independent and remained so until her death. It was part of her identity," she said.